Locking devices

ABSTRACT

Locking devices for sheet metal plugs and other hole closures, include at least one locking member which is hingedly connected to the disc and which includes a tab portion, which when struck an impacting blow, causes the locking member to rotate about its hinge into a position where the closure is locked in the hole.

United States Patent Boyer 14 July 18, 1972 54] LOCKING DEVICES 2,444,268 6/1948 Peters ..22o/27 2,501,722 3/1950 Hammerly et al. ...220/24.2 1 Invent Fred Boy", 5638 KOSW Avenue, N, 3,366,267 1/1968 Boyer ..220/27 Chicago, Ill. 60646 2,412,872 12/1946 Clark, Jr. ..220/24.2 X [22] Filed: May 18, 1970 I Primary Examiner-Raphael H. Schwartz 1 1 Appl- 38,290 Attorney-Molinare, Allegretti, Newitt & Witcoff [52] us. Cl .220/59, 220/242 1 1 ABSTRACT [51] Int. Cl. ..A47j 27/08 Locking devices for Sheet metal plugs and other hde closures [58] Field of ar h 9, 55 C, include at least one looking member which is hingedly con- 220/34, 3.5, 3.6; 292/253; 229/220; 217/69, 70; nected to the disc and which includes a tab portion, which 229/49, 5.7; 24/73 MF when struck an impacting blow, causes the locking member to rotate about its hinge into a position where the closure is [56] References Cited locked in the e,

UNITED STATES PATENTS 22 Claims, 27 Drawing Figures 2,682,693 7/1954 Poupitch ..24/73 MF Patented July 18, 1972 2 Sheets-Sheet l Patented July 18, 1972 3,677,434

2 Sheets-Sheet 2.

I 'Ex 741R FRED 5. BUYER BY mwzw a/w g ATTORNEYS LOCKING nsvrcss BACKGROUND AND SUMMARY OF THE INVENTION The present invention relates to locking devices and, more particularly, to locking devices for sheet metal closures and plugs.

Sheet metal closures and plugs frequently find use in the closing of openings in various sheet metal or cast metal boxes, such as conduit holes in electrical junction boxes, access openings to electrical terminals or mechanisms in appliances and the like. It is desirable that these plugs or closures are both simple to manufacture and to install with the minimum of time, effort and tools necessary for performing the installation. By way of example, an easily installed plug for an electrical junction box is described in my U.S. Pat. No. 3,366,267. That plug includes a plurality of tabs which extend from the plug at points spaced about the outer periphery thereof. To install the plug, it is simply positioned in the opening to be closed and the plug is then struck upon a creased chord so as to flatten to engage the tabs with the sheet metal box. The locking devices of the present invention are improvements over the devices shown in that patent.

The locking devices of the present invention as employed with closures, plugs or the like, may be quickly and easily moved to their locking position to lock the closure or plug in place with a minimum of time, effort and tools. The locking devices of the present invention are preferably captive fasteners which are part of a plate, cover or sheet metal assembly and have a wide variety of applications in assembly line products. The locking devices of the invention eliminate the need for the handling of screws, bolts and the like and may be employed with covers or plates which can cover openings having a variety of sizes and shapes and openings fonned in heavy gauge material as well as covers or plates which are angled, curved or wrap around. The locking devices of the present invention may be formed rapidly, easily and inexpensively directly from the closure or plug material as by stamping, cutting or the like. The locking devices of the present invention, in their unlocked position, are readily received through an opening or hole and once they are positioned in the opening, maybe quickly and easily moved to their locked position by the simple blow of an impacting tool. Moreover, once the locking devices of the present invention have been locked, they may be simply unlocked and their closure or plug removed from the opening without destruction of either the plugs or locking devices. A closure, plug or the like incorporating the principles of the invention may include means to align the closure or plug with the periphery of the opening and, in certain preferred embodiments, this alignment may be provided by a bead or tab which is formed as a part of the locking device of the invention. Several preferred embodiments of locking device of the invention may be readily employed to lock a closure of plug to a structure which is substantially greater in thickness than the closure or plug material. The locking devices of the invention are capable of firmly locking their closure or plug to the structure and yet present a smooth, flush external appearance after locking has been accomplished and are not subject to denting or other misshaping during locking. Finally, in a plug or closure constructed in accordance with the principles of the invention, either heavy or light gauge material may be employed without detracting from the ease of operation of the locking device.

In a preferred locking device of the invention, a locking member is formed on a plate member, the latter of which is adapted to be locked to a sheet material structure. The locking member includes a first tab which is normally spaced from one side of the plate member by a distance sufficient to receive the structure material therebetween and a second tab which is normally spaced from the other side of the plate member. Hinge means is associated with the locking member, such that the locking member is rotatable about the hinge means between a first position where the locking member is positioned at a substantial angle to the plane of the plate member and is unlocked from the structure material and a second position where the locking member is substantially parallel to the plate member and is in locking engagement with the structure material.

These and other objects, features and advantages of the present invenu'on will-be more clearly understood through a consideration of the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS In the course of this description, reference will frequently be made to the attached drawings in which:

FIG. 1 is a plan view and FIGS. 2 and 3 are cross sectioned elevation views of a closure plug, the latter views being taken substantially along line 2-2 of FIG. 1, and showing one preferred embodiment of locking device of the invention in the inserted, but unlocked, and in the locked positions, respectively;

FIG. 4 is a cross sectioned elevation view of a portion of the closure plug taken substantially along line 4-4 of FIG. 1 and showing the relationship of the alignment bead to the edge of the opening which the closure plug is to close;

FIG. 5 is a plan view and FIGS. 6-8 are cross sectioned elevation views of another embodiment of lockinG device, the latter views being taken substantially along line 6-6 of FIG. 5, and showing the locking device in unlocked, intermediate and locked positions, respectively;

FIG. 9 is a cross sectioned elevation view of the locking device of FIG. 5, as employed for locking the closure to sheet material having a substantially greater thickness than the thickness of the closure or plug;

FIG. 10 is a cross sectioned elevation view of another embodiment of locking device for locking to sheet material having a substantial thickness;

FIG. 11 is a cross sectioned elevation view of still another embodiment of locking device for locking to sheet material having a substantial thickness;

FIG. 12 is a plan view and FIGS. 13 and 14 are cross sectioned elevation views taken substantially along line 13-13 of FIG. 12 and showing another embodiment of locking device in the unlocked and locked positions, respectively;

FIG. 15 is a plan view and FIGS. 16 and 17 are cross sectioned elevation views taken substantially along line l6l6 of FIG. 15 and showing still another embodiment of locking device in the unlocked and locked positions, respectively;

FIG. 18 is a cross sectioned elevation view of another embodiment of locking device constructed in accordance with the principles of the invention;

FIG. 19 is a plan view of still another embodiment of locking device constructed in accordance with the principles of the invention;

FIG. 20 is a schematic view of a stamping press showing the locking device of FIG. 19 being formed;

FIG. 21 is a plan view and FIGS. 22 and 23 are elevation views which show still another embodiMent of locking device constructed in accordance with the principles of the invention, FIG. 23 being taken substantially along line 23-23 of FIG. 22;

FIG. 24 is a cross sectioned elevation view of another embodiment of locking device of the invention, and

FIGS. 25, 25A, and 25B are plan views of various configurations of closures or plugs in which the locking devices of the present invention have been arranged in various positions.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIGS. 1-4, one preferred embodiment of plug or closure locking device constructed in accordance with the principles of the invention is shown. The closure comprises a plate member or disc 10 which is stamped or formed in another suitable manner, fromsheet material, such as sheet metal. Such closure plug or disc may be readily employed, for example in the closure of conduit openings in the outer wall of an electrical junction box, as described in my above-mentioned prior patent.

One or more tabs 12 are formed about the perimeter of disc 10 as by stamping or the like. This tab 12 is bent from one side 14 of the disc 10 such that it is spaced from the side 14 by a distance sufiicient to enable receipt therebetween of the sheet material 16 of the structure to which the plug is to be locked.

A hinged locking member, generally 18, is also formed in spaced relationship to tab 12, preferably by stamping from the disc 10. The locking member 18 is stamped so as to form a pair of tabs 20 and 22. Tab 22 is preferably formed in this embodiment by stamping out an arcuate slot 24 to provide an opening of a size which is sufficient to accommodate the tab 22, as shown in FIG. 3, when the locking member is locked. After the locking member 18 has been formed, it is bent so as to be positioned in angular relationship to the plane of the disc 10, as shown in FIG. 2.

If desired, one or more arcuate alignment beads 26 may also be stamped in the disc 10 to insure accurate alignment of the locking members 18 with the edges 28 of the opening which the disc is to act as a closure for, as shown in FIG. 4.

In use, the disc 10 is simply positioned, tab 12 first, in the opening Since the locking member 18 is in the angular relation to the plane of the disc, as shown in FIG. 2, and also since the point at which tab 20 is attached to tab 22 is displaced from the pivot axis P toward the center of the disc as shown in FIGS. 1-3, its tab 20 will easily clear the edge 28 of the opening in the sheet material 16. Once the disc or plate member 10 is positioned in overlying and closing relationship to the opening, tab 22 need only be tapped lightly with a hammer or other impact instrument. Upon striking tab 22, the locking member 18 will pivot about the pivot axis P of the hinge provided by the interconnecting portions 30 of the sheet materials of the disc 10. Slot 24, as shown in FIG. 1, is preferably cut so as to extend beyond the inner end of tab 20 to reduce the likelihood of tearing of the portions 30 on pivoting of the locking member. Referring to FIG. 3, it will be seen that when the locking member 18 is rotated into its locked position, its tab 22 will re-enter the opening defined by slot 24 to again become substantially flush and coplanar with the plate of the disc 10.

In the remaining locking device embodiments to be described hereafter, certain components of these embodiments are identical or similar to the components of the embodiment just described. Accordingly, like reference numerals will be used to designate similar, but not necessarily identical components.

Referring to FIGS. -8, another embodiment of locking device is shown which differs from the last described embodiment in several respects. The first difference in this embodiment is that, rather than forming the tab 22 by slotting at 24 as shown in FIG. 1, the tab 22 is first punched or stamped from the opening 32 and then the opening is recessed about its periphery at 34 so as to form a downward extending bead 36 about the opening. This manner of construction serves at least two purposes, one of which is to provide a flush clean recess 34 in which the tab 22 of the locking member 18 may be easily received in flush accommodation with the disc 10. If the tab 22 is simply stamped from the sheet material of the disc, the opening 32 would have to be somewhat enlarged, such as by cutting the slot shown in FIG. 1, or the tab 22 must be reduced in size, since stamping tends to enlarge the tab 22 such that it will not refit properly back into the opening after stamping. By recessing the edge of the opening, not only is the tab 22 now able to be readily received in the recess 34 in flush relationship to the disc, but also dirt and other contamination is prevented from passing between the tab 22 and the edge of the opening 32. The bead 36 also eliminates the need for the alignment bead 26 shown in the previous embodiment, since the bead 36 itself acts to both strengthen and align the disc with the edge of the opening 28 as shown in FIG. 6.

In addition to the recessed opening of this embodiment, the angular relation of the tabs 20 and 22 to each other is slightly different than the tabs shown in FIGS. 1-3. Referring to FIG. 6, the locking member 18 is shown having just been inserted into the opening 28. Now when the tab 22 is tapped with the impacting instrument, such as a hammer, the locking member 18 is rotated about the pivot point P until tab 20 just contacts the underside of the edge of the opening. At this point, tab 22 will still extend upward slightly from the recess 34, as shown in FIG. 7. A slight additional tap of the hammer will now firmly seat tab 22 in recess 34, as shown in FIG. 8, and will effect a firm and secure locking of the tab 20 against the underside of the material 16.

Referring to FIGS. 9-11, three different embodiments of locking devices are shown being employed in the locking of a disc or plate member 10 to a structure which is formed of a sheet material which is substantially thicker than that of the disc or plate member. Again the pivot point of the locking member 18 is indicated as P and, in each of the embodiments, the locking member 18 is shown in one of three positions: (a) its just-inserted position; (b) a position in which it has been moved to just begin to contact the thick material; and (c) into a final position in which the tab 22 is positioned in flush relationship to the plate or disc 10. It will be understood when viewing FIGS. 9-11, that any one of several different thicknesses of sheet material 16 may be equally well employed with either of the locking devices, since once tab 20 of either embodiment contacts the sheet material, the closure or disc 10 will be locked thereto. Any further impacting force exerted upon tab 22 will simply bend that tab relative to tab 20 and into flush relationship with the disc.

Referring to FIGS. 12-14 another embodiment of locking device is shown which includes several features which difi'er from the embodiments previously described. In this embodiment tab 20 is wider than the impact tab 22. Since tab 20 is wider, the hinge of the locking member 18 of this embodiment is that bridging portion of material at 38. Thus the hinge axis P coincides more or less with the end of tab 22.

In addition, tab 22 is embossed, as shown in FIGS. 13 and 14. Embossing effects a reduction in the overall perimeter of tab 22 to enable the tab to re-enter the opening 40, as shown in FIG. 14. Embossing of tab 22 not only eliminates the need for the oversize slotting shown in FIG. 1 or the bead 36 of FIG. 5, but also serves to strengthen the tab 22.

A slot 42 may also be formed in the tab 22 for receiving a screw driver 44, whereby the locking device can be easily and simply unlocked from the position shown in FIG. 14 by insertion of a screw driver or other suitable tool into the slot.

Referring to FIGS. 15-17, another preferred embodiment of locking device is shown in which the portion of the sheet material of the disc 10 which is punched out to form a screw driver slot 42, is also utilized to form the locking tab 20 of the locking member 18. In this embodiment, the tab 22, when finally struck into its locking position, may lie upon the surface of the disc 10 as shown in FIG 17, or may be cut away or embossed as previously described. To define the pivot axis P and prevent progressive tearing of the tab 22, holes 46 are preferably drilled as shown in FIG. 15.

In FIG. 18, a locking device is shown which is similar in many respects to the locking device of FIGS. 15-17, but in which the tab 20 is welded to the underside of tab 22, rather than being punched therefrom as previously described. In addition, tab 12 is also attached to disc 10 by welding as shown.

Referring to FIGS. 19 and 20, an embodiment of locking device is shown which is particularly well adapted for use in closures having small diameters. In thiS embodiment, tabs 20 and 22, as shown in FIG. 19, are first formed by punching or stamping the locking member 18 from the sheet stock material 48. The material is then drilled at 46 and the locking member 18, which is formed by tabs 20 and 22, is then bent at an angle from the major plane of the sheet material, as shown in FIG. 20. The sheet material 48 is held upon a bed 50 by a clamp member 52 which is loaded in the direction shown by arrow a. Another member 54 is then brought down in the direction of arrow b to hit the top 56 of the tab 22 to cause the entire locking member 18 to move in the direction of arrow c. Such movement will cause the sheet material which fonns the disc to bulge slightly at 58, as shown in FIG. 19, but will allow the Referring to FIGS. 21-23, another embodiment of locking device is shown in which the locking member 18 pivots on a pivot axis P about the interconnecting sheet portions 60 5 between the tabs 20 and 22. In this embodiment, holes 62 and 64 are stamped to define tabs 20 and 22 respectively, the hinged portion 60 extending between the holes. The portion of the sheet material which is stamped from holes 62 to define the holes, is bent downward, as shown in FIGS. 22 and 23, to form opening alignment tabs 66.

Referring to FIG. 24, an embodiment of locking device is shown which is particularly suited for locking large covers or the like which might otherwise be easily dislodged or pulled loose if the cover buckles for one reason or another. In this embodiment, tabs 20 include an upturned tip 66 which projects into a corresponding hole 68 in the material 16 to interlock the cover and material 16 when the locking device is in the locked position. Thus, the possibility of lateral movement of the cover 10 relative to the material 16 is substantially reduced.

It will be understood that the locking devices of the invention may be employed to lock a variety of closure plates or plugs which may vary widely in either shape or thickness. Several different closure shapes and locking device positions are shown in FIGS. 25, 25A, and 25B.

It will also be understood that although various features It should also be understood that the embodiments of the present invention which have been described are merely illustrative of a few of the applications of the principles of the invention. Numerous modifications may be made by those skilled in the art without departing from the true spirit and scope of the invention.

1. A locking device for attaching a plate member to a structure comprising:

a plate member having a predetermined configuration,

at least one locking member on and adjacent an edge of the plate member, said locking member including a first tab which extends from one side of the plate member when said locking member is in a first position and which is adapted to receive the material of the structure therebetween, and a second tab interconnected with said first tab and which extends from the other side of the plate member when said locking member is in said first position, and

hinge means associated with said locking member for rotation of said locking member about a pivot axis thereof, said hinge means comprising portions of said plate member interconnecting said plate member with said locking member, said portions having at least a part thereof positioned laterally outward from one of said first and second tabs in a direction substantially parallel to Said pivot axis, said locking member being rotatable about the pivot axis of said hinge means independently of 65 said configuration of said plate member between said first position wherein said first tab is unlocked from said structure to a second position wherein said second tab is substan-tially parallel to said plate member and said first tab is in locking engagement with the material of said structure and extends toward said edge of said plate member.

2. The device of claim 1 wherein said second tab includes a 3. The device of claim 1 wherein said tabs are formed in integral one-piece relationship with said plate member.

4. The device of claim 1 wherein said second tab is positioned in an opening in said plate member when said locking member is in said second position, whereby said second tab and said plate member are substantially coplanar.

5. The device of claim 4 wherein said opening includes a beaded recess.

6. The device of claim 4 including alignment means ad- 10 jacent and associated with said opening for aligning the plate member relative to the structure material.

7. The device of claim 1 wherein said plate member comprises a disc and at least one of said locking members is positioned adjacent the perimeter of the disc.

8. The device of claim 7 wherein said locking member and the adjacent edge of said disc are deformed.

9. The device of claim 1, wherein said locking member is constructed and arranged to receive structure material of varying thickness between said first tab and said plate member.

10. The device of claim 1 wherein said second tab includes slot means therein.

11. The device of claim 10, wherein said slot means is formed by punching said first tab from said second tab.

12. The device of claim 1 wherein said second tab is embossed.

13. The device of claim 1 wherein, when said locking member is in said first position, said first and second tabs are disposed at angles from said plate member, the angle of said first tab being smaller than the angle of said second tab.

14. The device of claim 1 including interlocking means on said structure and said first tab which interlocks the structure and the plate member when said locking member is in said second position.

15. The device of claim 14 wherein said interlocking means comprises a bent tip on said first tab and a hole in the material of said structure positioned to receive said bent tip.

16. The device of claim 1 wherein said plate member and said locking member are formed of sheet material.

17. The device 0F claim 1 wherein said locking member includes opening means associated with said second tab for opening said locking member.

18. A locking device for attaching a plate member to a structure comprising;

a locking member on the plate member, said locking member including a first tab which is normally spaced from one side of the plate member by a distance sufiicient to receive the material of the structure therebetween, and a second tab interconnected with said first tab and which is normally spaced from the other side of the plate member, and

hinge means associated with said locking member, said locking member being rotatable about said hinge means between a first position wherein the locking member is at a substantial angle to the plane of the plate member and is unlocked from the structure material and to a second position wherein the locking member is substantially parallel to the plate member and is in locking engagement with the structure material, said tab being positioned in an opening in said plate member having a beaded recess about at least a part of its perimeter when said locking member is in said second position, whereby said second tab and said plate member are substantially coplanar.

19. A locking device for attaching a plate member to a structure comprising;

a locking member on the plate member, said locking member including a first tab which is normally spaced from one side of the plate member by a distance sufficient to receive the material of the structure therebetween, and a second tab interconnected with said first tab and which is normally spaced from the other side of the plate member,

hinge means associated with said locking member, said locking member being rotatable about said hinge means between a first position wherein the locking member is at a substantial angle to the plane of the plate member and is unlocked from the structure material and to a second position wherein the locking member is substantially parallel to the plate member and is in locking engagement with the structure material, and

interlocking means on said structure and said first tab which interlocks the structure and the plate member when said locking member is in said second position, said interlocking means including projecting means on one of said first tab and said material and a hole in the other one of said first tab and said material positioned to receive said projecting means.

20. The device of claim 19 wherein said projecting means comprises a bent tip on said first tab and said hole is in the material of said structure and positioned to receive said bent tip.

21. The locking device of claim 1 wherein said first and second tabs are interconnected to each other at a point spaced from the axis about which said locking member rotates toward the center of said plate member.

22. The locking device of claim 1 wherein said first and second tabs are movable relative to each other when said first tab is in engagement with said material and said second tab is moved relative to said plate member toward said substantially parallel position.

# i i i i 

1. A locking device for attaching a plate member to a structure comprising: a plate member having a predetermined configuration, at least one locking member on and adjacent an edge of the plate member, said locking member including a first tab which extends from one side of the plate member when said locking member is in a first position and which is adapted to receive the material of the structure therebetween, and a second tab interconnected with said first tab and which extends from the other side of the plate member when said locking member is in said first position, and hinge means associated with said locking member for rotation of said locking member about a pivot axis thereof, said hinge means comprising portions of said plate member interconnecting said plate member with said locking member, said portions having at least a part thereof positioned laterally outward from one of said first and second tabs in a direction substantially parallel to said pivot axis, said locking member being rotatable about the pivot axis of said hinge means independently of said configuration of said plate member between said first position wherein said first tab is unlocked from said structure to a second position wherein said second tab is substan-tially parallel to said plate member and said first tab is in locking engagement with the material of said structure and extends toward said edge of said plate member.
 2. The device of claim 1 wherein said second tab includes a force receiving surface whereby said locking member moves from said first to said second position when a force is exerted on said surface.
 3. The device of claim 1 wherein said tabs are formed in integral one-piece relationship with said plate member.
 4. The device of claim 1 wherein said second tab is positioned in an opening in said plate member when said locking member is in said second position, whereby said second tab and said plate member are substantially coplanar.
 5. The device of claim 4 wherein said opening includes a beaded recess.
 6. The device of claim 4 including alignment means adjacent and associated with said opening for aligning the plate member relative to the structure material.
 7. The device of claim 1 wherein said plate member comprises a disc and at least one of said locking members is positioned adjacent the perimeter of the disc.
 8. The device of claim 7 wherein said locking member and the adjacent edge of said disc are deformed.
 9. The device of claim 1, wherein said locking member is constructed and arranged to receive structure material of varying thickness between said first tab and said plate member.
 10. The device of claim 1 wherein said second tab includes slot means therein.
 11. The device of claim 10, wherein said slot means is formed by punching said first tab from said second tab.
 12. The device of claim 1 wherein said second tab is embossed.
 13. The device of claim 1 wherein, when said locking member is in said first position, said first and second tabs are disposed at angles from said plate member, the angle of said first tab being smaller than the angle of said second tab.
 14. The device of claim 1 including interlocking means on said structure and said first tab which interlocks the structure and the plate member when said locking member is in said second position.
 15. The device of claim 14 wherein said interlocking means comprises a bent tip on said first tab and a hole in the material of said structure positioned to receive said bent tip.
 16. The device of claim 1 wherein said plate member and said locking member are formed of sheet material.
 17. The device oF claim 1 wherein said locking member includes opening means associated with said second tab for opening said locking member.
 18. A locking device for attachIng a plate member to a structure comprising; a locking member on the plate member, said locking member including a first tab which is normally spaced from one side of the plate member by a distance sufficient to receive the material of the structure therebetween, and a second tab interconnected with said first tab and which is normally spaced from the other side of the plate member, and hinge means associated with said locking member, said locking member being rotatable about said hinge means between a first position wherein the locking member is at a substantial angle to the plane of the plate member and is unlocked from the structure material and to a second position wherein the locking member is substantially parallel to the plate member and is in locking engagement with the structure material, said tab being positioned in an opening in said plate member having a beaded recess about at least a part of its perimeter when said locking member is in said second position, whereby said second tab and said plate member are substantially coplanar.
 19. A locking device for attaching a plate member to a structure comprising; a locking member on the plate member, said locking member including a first tab which is normally spaced from one side of the plate member by a distance sufficient to receive the material of the structure therebetween, and a second tab interconnected with said first tab and which is normally spaced from the other side of the plate member, hinge means associated with said locking member, said locking member being rotatable about said hinge means between a first position wherein the locking member is at a substantial angle to the plane of the plate member and is unlocked from the structure material and to a second position wherein the locking member is substantially parallel to the plate member and is in locking engagement with the structure material, and interlocking means on said structure and said first tab which interlocks the structure and the plate member when said locking member is in said second position, said interlocking means including projecting means on one of said first tab and said material and a hole in the other one of said first tab and said material positioned to receive said projecting means.
 20. The device of claim 19 wherein said projecting means comprises a bent tip on said first tab and said hole is in the material of said structure and positioned to receive said bent tip.
 21. The locking device of claim 1 wherein said first and second tabs are interconnected to each other at a point spaced from the axis about which said locking member rotates toward the center of said plate member.
 22. The locking device of claim 1 wherein said first and second tabs are movable relative to each other when said first tab is in engagement with said material and said second tab is moved relative to said plate member toward said substantially parallel position. 